[lib/Object] - Introduce Decompressor class.

Decompressor intention is to reduce duplication of code.
Currently LLD has own implementation of decompressor
for compressed debug sections.

This class helps to avoid it and share the code.
LLD patch for reusing it is D28106

Differential revision: https://reviews.llvm.org/D28105

llvm-svn: 291675

1 files changed, 12 insertions, 66 deletions

diff --git a/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp b/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
index 7df66c76e8b..77f6f65ee13 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
@@ -14,6 +14,7 @@
 #include "llvm/DebugInfo/DWARF/DWARFDebugArangeSet.h"
 #include "llvm/DebugInfo/DWARF/DWARFDebugPubTable.h"
 #include "llvm/DebugInfo/DWARF/DWARFUnitIndex.h"
+#include "llvm/Object/Decompressor.h"
 #include "llvm/Object/MachO.h"
 #include "llvm/Object/RelocVisitor.h"
 #include "llvm/Support/Compression.h"
@@ -577,66 +578,6 @@ DWARFContext::getInliningInfoForAddress(uint64_t Address,
   return InliningInfo;
 }
 
-static bool consumeCompressedGnuHeader(StringRef &data,
-                                       uint64_t &OriginalSize) {
-  // Consume "ZLIB" prefix.
-  if (!data.startswith("ZLIB"))
-    return false;
-  data = data.substr(4);
-  // Consume uncompressed section size (big-endian 8 bytes).
-  DataExtractor extractor(data, false, 8);
-  uint32_t Offset = 0;
-  OriginalSize = extractor.getU64(&Offset);
-  if (Offset == 0)
-    return false;
-  data = data.substr(Offset);
-  return true;
-}
-
-static bool consumeCompressedZLibHeader(StringRef &Data, uint64_t &OriginalSize,
-                                        bool IsLE, bool Is64Bit) {
-  using namespace ELF;
-  uint64_t HdrSize = Is64Bit ? sizeof(Elf64_Chdr) : sizeof(Elf32_Chdr);
-  if (Data.size() < HdrSize)
-    return false;
-
-  DataExtractor Extractor(Data, IsLE, 0);
-  uint32_t Offset = 0;
-  if (Extractor.getUnsigned(&Offset, Is64Bit ? sizeof(Elf64_Word)
-                                             : sizeof(Elf32_Word)) !=
-      ELFCOMPRESS_ZLIB)
-    return false;
-
-  // Skip Elf64_Chdr::ch_reserved field.
-  if (Is64Bit)
-    Offset += sizeof(Elf64_Word);
-
-  OriginalSize = Extractor.getUnsigned(&Offset, Is64Bit ? sizeof(Elf64_Xword)
-                                                        : sizeof(Elf32_Word));
-  Data = Data.substr(HdrSize);
-  return true;
-}
-
-static bool tryDecompress(StringRef &Name, StringRef &Data,
-                          SmallString<32> &Out, bool ZLibStyle, bool IsLE,
-                          bool Is64Bit) {
-  if (!zlib::isAvailable())
-    return false;
-
-  uint64_t OriginalSize;
-  bool Result =
-      ZLibStyle ? consumeCompressedZLibHeader(Data, OriginalSize, IsLE, Is64Bit)
-                : consumeCompressedGnuHeader(Data, OriginalSize);
-
-  if (!Result || zlib::uncompress(Data, Out, OriginalSize) != zlib::StatusOK)
-    return false;
-
-  // gnu-style names are started from "z", consume that.
-  if (!ZLibStyle)
-    Name = Name.substr(1);
-  return true;
-}
-
 DWARFContextInMemory::DWARFContextInMemory(const object::ObjectFile &Obj,
     const LoadedObjectInfo *L)
     : IsLittleEndian(Obj.isLittleEndian()),
@@ -660,18 +601,23 @@ DWARFContextInMemory::DWARFContextInMemory(const object::ObjectFile &Obj,
     if (!L || !L->getLoadedSectionContents(*RelocatedSection,data))
       Section.getContents(data);
 
-    name = name.substr(name.find_first_not_of("._")); // Skip . and _ prefixes.
-
-    bool ZLibStyleCompressed = Section.isCompressed();
-    if (ZLibStyleCompressed || name.startswith("zdebug_")) {
+    if (Decompressor::isCompressed(Section)) {
+      Expected<Decompressor> Decompressor =
+          Decompressor::create(name, data, IsLittleEndian, AddressSize == 8);
+      if (!Decompressor)
+        continue;
       SmallString<32> Out;
-      if (!tryDecompress(name, data, Out, ZLibStyleCompressed, IsLittleEndian,
-                         AddressSize == 8))
+      if (auto Err = Decompressor->decompress(Out))
         continue;
       UncompressedSections.emplace_back(std::move(Out));
       data = UncompressedSections.back();
     }
 
+    // Compressed sections names in GNU style starts from ".z",
+    // at this point section is decompressed and we drop compression prefix.
+    name = name.substr(
+        name.find_first_not_of("._z")); // Skip ".", "z" and "_" prefixes.
+
     StringRef *SectionData =
         StringSwitch<StringRef *>(name)
             .Case("debug_info", &InfoSection.Data)